This invention relates to a control system for an aircraft control surface using multiple hydraulic jacks and a process for management of the operation of control surface actuation jacks.
The process according to the invention may be used on aircraft, particularly on commercial transport aircraft and supersonic aircraft. For example, it may be applied to trailing edge control surfaces such as riders, elevators or ailerons, or to any other control surface on the aircraft.
In general, aircraft control surfaces are activated by several servo-controlled actuators and are energized by one or several hydraulic circuits.
An aircraft may be equipped with a number of hydraulic circuits pressurized through proportion units. It may also be equipped with stand alone hydraulic circuit pressurized by an electric pump. Actuators may comprise one or several hydraulic jacks. In this respect, refer to documents (1) and (2), the reference of which are given at the end of this description.
The number and dimensions of jacks are determined as a function of the maximum aerodynamic loads that may be exerted on the corresponding control surfaces.
Furthermore, the hydraulic flow necessary to maneuver the control surfaces is proportional to the amplitude and displacement speed of the control surfaces.
But the movement amplitude of control services and the movement speed are usually maximum during take off and landing phases.
During this flight phases, a number of other actuators such as actuators governing the retraction or extension of a landing gear also require a large hydraulic flow.
The result is that aircraft hydraulic circuits need to be very conservatively designed, in order to provide the large hydraulic flows necessary during the landing and take off phases. Consequently, hydraulic circuits create size and weight problems.
The purpose of this invention is to propose a control system for an aircraft control surface capable of operating with reduced hydraulic circuits, while being capable of maneuvering control surfaces under flight conditions in which aerodynamic loads are maximum.
Another purpose is to propose a control system that can operate with a reduced hydraulic flow during the take off and landing phases, in other words particularly when starting operation with other equipment such as landing gear, that also consume hydraulic power.
Another purpose is to propose this type of system in which actuators may be laid out more easily in thin profiles such as wing elements, minimizing the size of fairings.
In order to achieve these purposes, the purpose of the invention is more particularly a control system for an aircraft control surface comprising at least one control service actuator equipped with at least two power jacks capable of operating according to at least one activated mode and one deactivated mode. According to the invention, the control system comprises a control unit capable of making a number of jacks operate in an active mode depending on aircraft flight conditions. In particular, the control unit may be designed to determine a force to be exerted on the control surface, and be connected to the said actuator to make a number of jacks depending on the said force to be exerted, in an activated mode.
The control surface is maneuvered by one or several actuators that may be connected to different hydraulic circuits on the aircraft, respectively.
An activated mode is a power jack operation mode in which the power jack actively participates in moving a control surface by exerting forces causing clearance on the control surface. In the case of a hydraulic jack with two chambers, the chambers are then connected to a hydraulic power source such as a hydraulic circuit providing energy to the jack to actuate the control surface.
Deactivated mode is an operating mode in which the power jack forms the movement of the control surface without provoking it. In the case of a hydraulic jack, the jack chambers are then usually connected to each other through a restrictor to absorb the movement of the control surface.
When forces to be exerted on the control surface are small, which is typically the case when the aircraft speed is low, only a small number of jacks provided on at least one actuator, for example a single jack, may be used in the activated mode.
Thus, according to the invention, during take off landing when the amplitude and displacement speed of the control surfaces are large but the force to be exerted is small, only a small number of jacks equipping an actuator may be energized.
In the case of hydraulic jacks used on an actuator, the fact that only a small number jacks are linked to the hydraulic circuit powering this actuator means that only a small flow of pressurized fluid is necessary. Therefore some of the hydraulic energies are available for other equipment such as actuator jacks for extending or retracting landing gear.
Conversely, when forces to be exerted are high, in other words at high aircraft speed, a larger number, or all of the jacks equipping at least one actuator may be controlled to operate in activated mode.
High aircraft speeds are reached during the xe2x80x9ccruisingxe2x80x9d0 flight phase. During this flight phase, forces to be exerted on control surfaces are high, but the amplitude and movement speed of the control surfaces are usually low. In the case of hydraulic jacks, all jacks used in an actuator that can then be connected to the hydraulic circuit powering this actuator without requiring an excessive fluid flow.
Thus, according to the invention, small hydraulic systems can be used and the jacks equipping an actuator are small and can be housed in smaller sized fairing or thin profiles. These advantages are particularly useful for supersonic aircraft.
According to one particular embodiment of the system according to the invention, the control unit is connected to a control surface position sensor and to a control device. It may then comprise a programmed computer to determine a minimum number of jacks equipping at least one actuator and necessary to cause movement of the control surface with an amplitude corresponding to a control order originating from the control device.
Alternatively, the control unit may also be combined with flight control order calculation and generation means depending on specific flight phases. The control unit is then designed to associate a given number of jacks equipping an actuator depending on activated mode, for each flight phase.
The means of calculating and generating flight control order may comprise an aircraft computer equipped with one or more redundant calculation units. For example, this type of computer can make a distinction between flight phases such as take off, initial claim, cruising phase, descending phase, approach phase and finally taxing.
A certain number of jacks equipping an actuator to operate in activated mode, and a number of jacks operating in deactivating mode, can be associated with each flight phase in a determined manner.
For example, the computer may be programmed for a given control surface, so as to operate single jack for a given actuator in activated mode during take off from taxing phases, or to operate two jacks in the initial climb and approach phases, and to make three jacks operate in the cruising and descending phases.
According to another variant embodiment of the system according to the invention, the control unit may also be associated with means of measuring an aircraft speed and may be designed to operate a number of jacks that increases with the aircraft speed for a given actuator, in activated mode.
In this case, the control unit may be programmed to operate a single jack in the aircraft low speed range for a given actuator, and to make two or more jacks operate in the mean and high speed ranges.
As mentioned previously, forces to be exerted on control surfaces are higher at high speeds, and therefore it is desirable that a large number of jacks should operate in activated mode. However, activation of large number of jacks does not require a large hydraulic flow to the extent that the movement of control surfaces is usually low at high aircraft speeds and takes place at low speed.
Within a low aircraft speed range, in which a high movement amplitude and hydraulic flow are necessary, but in which forces to be supplied are moderate, a small number of jacks equipping an actuator may be activated.
In the particular embodiment of actuators of a control surface, the actuators may comprise control blocks associated with jacks equipping them, these blocks being controlled from the control unit, in order to selectively make jacks operate according to an activated mode or a deactivated mode.
For example, for hydraulic jacks that comprise two jacks chambers separated by a mobile piston, control blocks may comprise mode drawers in order to selectively connect jack chambers to at least one hydraulic power source in activated mode, and to connect jack chambers to each other possibly through a restrictor, in deactivated mode.
The mode drawer may be associated with each jacks equipping an actuator.
According to one particular aspect of the invention, at least one of the jacks equipping an actuator may be associated with the three position mode drawer in order to form a passage between jack chambers in deactivated mode, to connect jack chambers to a hydraulic circuits through a servo-valve in a first activated mode, and to connect jack chambers to an electro-hydrostatic module forming a local and stand alone hydraulic power source in a second activated mode.
According to another particular aspect of the invention, an actuator may comprise at least two jacks each equipped with the mode drawer, in which at least one of the jacks is associated with the servo valve connected to the hydraulic circuit that forms a first hydraulic power source, and in which at least one of the jacks is associated with a stand alone electro-hydrostatic module forming a second local hydraulic power source.
The invention also relates to a control process for an aircraft control surface equipped with at least one actuator equipped with at least two jacks that can operate selectively in activated mode or deactivated mode. According to this process, in activated mode, the number of jacks that are made to operate depend on the aircraft speeds, or other particular conditions such as the flight phase.
In one particular embodiment of the process, a single jack equipping at least one actuator can be operated in activated mode when the aircraft speed is within a first low speed range, and two or more jacks equipping at least one actuator can be operated when the aircraft speed is in a second speed range greater than the speed in the first range.
As mentioned before, the said number of jacks to be activated can be determined as a function of the flight phase corresponding to determined speed.
Finally, a number of jacks equipping an actuator depending on the force to be exerted on the control surface to obtain a required movement, can be operated selectively in an activated mode or a deactivated mode.
Other characteristics and advantages of the invention will become clear from the following description with respect to figures in the attached drawings. This description is provided for illustrative purposes only, and is in no way restrictive.